The diesel or high compression ignition internal combustion engine in common usage presently is usually mechanically operated from the governor to the rack mechanism which controls the amount of fuel injected to the cylinders. Recent electrical or electronic systems utilized in several diesel engines have been constant pressure devices where an electrical pulse actuates a solenoid valve which allows the constant pressure to force fuel into the cylinder as long as the solenoid was activated. However, most present systems utilize a jerk pump injector which mechanically operates from a push rod whereby pressure varies with speed as does the time of injection. Since the use of a jerk pump injector for fuel injection is more accurate for injecting the fuel than are the constant pressure devices, the present invention substitutes an electronic control of a spill valve for the mechanical rack control but retains the jerk pump for pressure control.
Although electronic control systems for fuel injection systems are quite common in the prior art, the majority of these systems control the fuel pulse duration as a function of time and not a specific number of degrees per engine revolution. Representative of the stateof-the-art are U.S. Pat. Nos. 3,653,365 to Monpetit; 3,659,571 to Lang and 3,800,749 to Advenier. The patent to Monpetit describes an electronic control system for a diesel engine whereby the system is controlled by the rotation of the engine providing a sawtooth wave, the slope of which is dependent upon the speed of rotation.
The patent to Lang shows an electronic speed regulating arrangement for diesel engines whereby input pulses are produced having a duration which is made variable corresponding to a predetermined speed-load characteristic of the engine. Input pulses from a monostable multivibrator have a duration which is a function of the speed of the engine. These input pulses, along with a secured set of pulses having a duration as a function of the state of the injector valve, are fed to a comparator and are made variable corresponding to a predetermined speed-load characteristic. The patent to Advenier teaches an apparatus for regulating the duration of a square wave signal in an electronic injection control installation for diesel engines. The circuitry includes a pulse generator slaved to the rotation of the engine for initiating each injection period and a function generator for developing a reference voltage. A rectangular delay signal is produced to develop a regulating voltage rising from zero until it corresponds to the instantaneous value of the reference voltage and then follows this value. The duration of the injection signal is a function of this regulating voltage. Each of these patents determine the fuel pulse as a function of time. Conversely, none of these patents determine the duration of the fuel pulse for a diesel or spark ignition internal combustion engine as a function of the amount of degrees of engine crankshaft rotation.